Motor

ABSTRACT

A motor includes a rotor part having a rotor shaft and a rotor magnet, a stator part oppositely disposed to the rotor magnet via a gap space, a bearing rotatably supporting the rotor shaft, a spring member abutting with one end of the rotor shaft to urge the rotor shaft in an axial direction. A spring member side restricting part is provided in the spring member to prevent fluctuation in the radial direction of the rotor shaft and a rotor shaft side restricted part is provided in the rotor shaft and engages with the spring member side restricting part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Application No. 2004-187626filed Jun. 25, 2004 and Japanese Application No. 2004-314148 filed Oct.28, 2004, which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a motor in which one end of a rotorshaft is urged by a spring member in its axial direction.

BACKGROUND OF THE INVENTION

A conventional motor 100 includes a rotor part 101 having a rotor shaft103 and a rotor magnet 104 and a stator part 102 which is disposed so asto face the rotor magnet 104 through a clearance as shown in FIG. 5. Therotor shaft 103 is rotatably supported by bearings 105, 110 and one endof the rotor shaft 103 is urged by a plate spring 107 in an axialdirection through a ball 108.

The bearing 105 includes a ball 105 a abutting with a fitting hole whichis formed on the other end of the rotor shaft 103 and a ball holdingbody 105 b for holding the ball 105 a. The bearing 110 is a radialbearing for supporting the rotor shaft 103 in a radial direction and isdisposed on the under side of the rotor magnet 104 in FIG. 5. Aclearance is formed between the inner peripheral face of the bearing 110and the outer peripheral face of the rotor shaft 101, and thus the rotorshaft 101 rotates smoothly without being locked (see Japanese PatentLaid-Open No. Hei 9-135562).

However, in the motor 100 shown in FIG. 5, the fluctuation occurs in therotor shaft 101 due to the positioning errors or the like between therotor magnet 104 and the stator part 102 when the motor is rotated, andnoises are generated between the bearings 110, 105 or the like and therotor shaft 103. It has been known that these noises are two differenttypes of noise, i.e., striking noise and sliding noise.

The striking noise has been considered to be generated by the rotorshaft 101 that moves radially due to the clearance formed between theinner peripheral face of the bearing 110 and the outer peripheral faceof the rotor shaft 103 and the rotor shaft 103 that strikes against theinner peripheral face of the bearing 110. When the rotor shaft 103strikes the bearing 110, a rattling sound is generated. This indicatesthe generation of the striking noise. The sliding noise is considered tobe generated when the ball 105 a integrally rotated with the rotor shaft103 slides to the ball holding body 105 b and when the ball 108integrally rotated with the rotor shaft 103 slides to the plate spring107. Further, the sliding noise is considered to be generated betweenthe rotor shaft 103 and the bearing 110 when the rotor shaft 103 isrotated.

SUMMARY OF THE INVENTION

It has been found that the occurrence of the striking noise can berestrained by regulating and preventing the fluctuation of the rotorshaft in the radial direction. Although the sliding noise may increase alittle, overall the noises are reduced during the rotation of the motormore than before. Therefore, it is an object and advantage of thepresent invention to provide a motor which is capable of restraining theoccurrence of the striking noise by regulating and preventing thefluctuation of the rotor shaft in the radial direction.

In order to achieve the above object and advantage, according to anembodiment of the present invention, there is provided a motor includinga rotor part having a rotor shaft and a rotor magnet, a stator partwhich is oppositely disposed to the rotor magnet via a gap space, abearing which rotatably supports the rotor shaft, a spring member whichabuts with one end of the rotor shaft to urge the rotor shaft in anaxial direction, a spring member side restricting part which is providedin the spring member to prevent the fluctuation in the radial directionof the rotor shaft, and a rotor shaft side restricted part which isprovided in the rotor shaft and engages with the spring member siderestricting part.

In accordance with an embodiment of the present invention, a springmember side restricting part is provided in the spring member to preventthe fluctuation in the radial direction of the rotor shaft and a rotorshaft side restricted part that engages with the spring member siderestricting part is provided in the rotor shaft. Therefore, even whenthe rotor shaft is fluctuated in the radial direction, the fluctuationin the radial direction of the rotor shaft is regulated by both thespring member side restricting part and the rotor shaft side restrictedpart, and thus the vibration can be restrained and the occurrence of thestriking noise can be restrained.

In accordance with an embodiment of the present invention, a sphericalrecessed part is formed in one of the rotor shaft side restricted partand the spring member side restricting part, and a spherical protrudedpart is formed in the other rotor shaft side restricted part and thespring member side restricting part. For example, the spring member siderestricting part may be formed with the spherical recessed part and therotor shaft side restricted part may be formed with the sphericalprotruded part. In this case, the diameter of the spherical recessedpart of the spring member side restricting part is preferably set to belarger than the diameter of the spherical protruded part of the rotorshaft side restricted part. According to the construction describedabove, a type of aligning function can be obtained in which theirrespective axial centers are shifted so as to coincide with each other.As a result, the fluctuation of the rotor shaft can be converged in therestraining direction by using the rotor shaft side restricted part andthe spring member side restricting part, and thus the vibration can besecurely restrained and the occurrence of the striking noise can berestrained. In addition, the rotor shaft side restricted part is easilyworked to the spherical protruded part and the spherical recessed partis easily formed in the spring member side restricting part. Therefore,additional component parts are not needed, and the rotor shaft siderestricted part and the spring member side restricting part can besimply worked without requiring a special tool and can be formed at alow cost.

Further, in accordance with an embodiment of the present invention, thespring member preferably urges the rotor shaft in the radial direction.In order to obtain this construction, the spring member side restrictingpart may abut with the rotor shaft side restricted part at a positiondeviated from the shaft center line of the rotor shaft. Concretely, thespring member side restricting part preferably abuts with the rotorshaft side restricted part at a position deviated about angle θ=20° inthe radial direction from the shaft center line of the rotor shaft.Since the rotor shaft is urged by the spring member in the radialdirection, the fluctuation of the rotor shaft is regulated along thedirection contacting with the spring member, and thus its vibration isrestrained and the occurrence of the striking noise can be restrained.

Further, in accordance with an embodiment of the present invention, thespring member side restricting part urges the rotor shaft siderestricted part in the axial direction of the rotor shaft. Concretely,the rotor shaft side restricted part may be formed in a spherical shapeand the abutting part of the spring member side restricting part withthe rotor shaft side restricted part may be formed in a V-shaped part, aspherical recessed part, an aperture part or a circular ring member.Alternatively, the rotor shaft side restricted part may be formed in aspherical recessed part and the spring member side restricting part maybe formed in a spherical protruded part. According to the constructiondescribed above, the fluctuation of the rotor shaft is regulated by thespring member side restricting part and the rotor shaft side restrictedpart, and thus its vibration is restrained and the occurrence of thestriking noise can be restrained. In addition, when the rotor shaft siderestricted part is urged by the spring member side restricting part inthe axial direction of the rotor shaft, the spring member siderestricting part may abut with the rotor shaft (rotation sidecontrolling part) at the position of or near the rotational center lineof the rotor shaft. Therefore, the starting torque required to start themotor at stopping can be reduced and the starting performance of themotor can be improved.

Further, in accordance with an embodiment of the present invention, thespring member is preferably provided with a bent part for adjusting aposition where the spring member side restricting part abuts with therotor shaft side restricted part. When the spring member is providedwith the bent part which is formed by bending a spring part, theposition of the spring member side restricting part abutting with therotor shaft can be adjusted if necessary. The bent part can be easilyformed at a low cost.

As described above, the motor in accordance with the embodiment of thepresent invention includes a rotor part having a rotor shaft and a rotormagnet, a stator part which is oppositely disposed to the rotor magnetvia a gap space, a bearing which rotatably supports the rotor shaft, aspring member which abuts with one end of the rotor shaft to urge therotor shaft in an axial direction, a spring member side restricting partwhich is provided in the spring member to prevent the fluctuation in theradial direction of the rotor shaft, and a rotor shaft side restrictedpart which is provided in the rotor shaft and engages with the springmember side restricting part. Therefore, even when the rotor shaft isfluctuated in the radial direction, the fluctuation in the radialdirection of the rotor shaft is regulated by both the spring member siderestricting part and the rotor shaft side restricted part, and thus thevibration can be restrained and the occurrence of the striking noise canbe restrained.

Other features and advantages of the invention will be apparent from thefollowing detailed description, taken in conjunction with theaccompanying drawings that illustrate, by way of example, variousfeatures of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a schematic structure of a motor inaccordance with a first embodiment of the present invention.

FIG. 2 is an enlarged view showing a rotor shaft side restricted partand a spring member side restricting part in accordance with the firstembodiment of the present invention.

FIGS. 3(a) through 3(d) are enlarged views showing a rotor shaft siderestricted part and a spring member side restricting part in accordancewith other embodiments of the present invention.

FIGS. 4(a) through 4(d) are enlarged views showing a rotor shaft siderestricted part and a spring member side restricting part in accordancewith other embodiments of the present invention.

FIG. 5 is a sectional view showing a schematic structure of aconventional motor.

FIG. 6 is an enlarged view showing a rotor shaft side restricted partand a spring member side restricting part in accordance with a secondembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A motor in accordance with an embodiment of the present invention willbe described below with reference to the accompanying drawings. FIG. 1is a sectional view showing a schematic structure of a motor inaccordance with a first embodiment of the present invention. FIG. 2 isan enlarged view showing a rotor shaft side restricted part and a springmember side restricting part in accordance with the first embodiment ofthe present invention.

A motor 1 in accordance with the first embodiment of the presentinvention shown in FIG. 1 includes a rotor part 2 having a rotor shaft 4and a rotor magnet 5 and a stator part 3 which is oppositely disposed soas to face the rotor magnet 5 through a clearance. The rotor shaft 4 isrotatably supported by bearings 6 and 7 and urged by a spring member 8that abuts with one end of the rotor shaft 4 in an axial direction.

The rotor magnet 5 is fixed to the rotor shaft 4 constructing the rotorpart 2 with an adhesive. The rotor magnet 5 is comprised of two piecesof approximately cylindrical permanent magnets 51, 52. In the firstembodiment of the present invention, the two pieces of permanent magnets51, 52 are formed, for example, of a rare earth permanent magnet ofNd—Fe—B system.

A recess in a circular shape is formed on both end faces of thepermanent magnets 51, 52 in the axial direction. This recess makes theweight of the permanent magnets 51, 52 lighter in weight. The moment ofinertia of the rotor magnet 5 is reduced by means of being lightweighted as described above.

The other end of the rotor shaft 4 is fixed by press fitting or with anadhesive to a fitting hole 10 b of a shaft 10 on which a lead screw partis formed. The lead screw part is engaged with a body to be fed notshown in the drawing.

The stator part 3 is constructed in a two-phase structure by using afirst stator core 31 and a second stator core 32 which is adjacentlyfixed to the first stator core 31 in the axial direction. Each of thefirst and the second stator cores 31, 32 is structured such that aplurality of pole teeth of the first or the second stator cores 31, 32are alternately disposed.

Circular ring-shaped coil bobbins 33, 34 are respectively disposed onthe outer peripheral faces of the respective pole teeth in the first andthe second stator cores 31, 32. Coils 35, 36 are wound around the bodypart of the circular ring-shaped coil bobbins 33, 34 and the terminalsof the coils 35, 36 are connected to terminal pins 37 that areintegrally provided in the coil bobbins 33, 34.

The first stator core 31 is housed in a motor case 38 and the secondstator core 32 is similarly housed in a motor case 39. The first and thesecond stator cores 31, 32 and the motor cases 38, 39 are concentricallydisposed on the axial line of the rotor shaft 4 as shown in FIG. 1 andfixed by welding.

The motor case 38 is fixed by welding to an erected part 9 a which isformed in a frame 9 as shown in FIG. 1. An erected part 9 b is alsoformed in the frame 9 and the bearing 7 is press-fitted to the erectedpart 9 b for rotatably supporting the shaft 10 on which the lead screwpart is formed.

The bearing 7 includes a ball 71 abutting with a fitting hole 10 aformed at the tip end of the shaft 10 and a ball holding body 72 whichholds the ball 71.

The bearing 6 is formed of resin having a lubricating property androtatably supports one end of the rotor shaft 4 in the radial direction.As shown in FIG. 2, bearing 6 for supporting the rotor shaft 4 in theradial direction (hereinafter, referred to as “radial bearing 6”) isformed with a bearing part 61 for supporting the rotor shaft 4 to beinserted, a press fitting part 62 which is press-fitted and fixed to theinner diameter face of the second stator core 32, and a flange part 63which is formed with one part of the outer peripheral part of thebearing 6 being protruded in the radial direction.

The bearing part 61 is disposed so as to be positioned in a recessedpart which is formed on the rotor magnet 5 to reduce the dimension ofthe entire motor 1 in the axial direction. In addition, the size of theinner diameter of the bearing part 61 is set to form a clearance withrespect to the outer diameter of the rotor shaft 4. The flange part 63is placed on the second stator core 32 to perform the positioning of thebearing 6 in the axial direction.

The spring member 8 is formed from one piece of a metal plate andincludes a spring part 81 abutting with one end of the rotor shaft 4 anda center hole 82. Further, the spring member 8 is fixed at a prescribedposition of the motor case 39 by welding.

The spring part 81 abuts with the one end of the rotor shaft 4 at aposition deviated from the shaft center line 4 a of the rotor shaft 4 asshown in FIG. 2. In other words, the spring part 81 urges the rotorshaft 4 in the axial direction and in the radial direction such that apart of the outer peripheral face of the rotor shaft 4 is brought intocontact with the inner peripheral face of a part of the bearing part 61of the radial bearing 6. For example, in the first embodiment of thepresent invention, the spring part 81 abuts with the rotor shaft 4 at aposition of about angle θ=20° deviated from the shaft center line 4 a inthe radial direction. However, the present invention is not limited tothe angle θ=20°. According to the construction described above, sincethe rotor shaft 4 is urged by a spring in the radial direction, thefluctuation of the rotor shaft 4 is regulated in the contactingdirection and the vibration is restrained, and thus the occurrence ofstriking noise is restrained.

Next, the regulation of the fluctuation of the rotor shaft 4 in theradial direction by the rotor shaft side restricted part 42 and thespring member side restricting part 83 will be described below withreference to FIG. 2.

The rotor shaft side restricted part 42 is a spherical protruded partformed at the one end of the rotor shaft 4. The spring member siderestricting part 83 is a spherical recessed part formed on the tip endside of the spring part 81. The center of the spherical protruded partof the rotor shaft side restricted part 42 coincides with the shaftcenter line 4 a of the rotor shaft 4. In addition, the diameter of thespherical recessed part of the spring member side restricting part 83 isset to be larger than that of the spherical protruded part of the rotorshaft side restricted part 42. In other words, the abutting area is setto become a point contact and a line contact to reduce their contactingarea and thus a sliding loss and a sliding noise are restrained.

In the first embodiment of the present invention, the rotor shaft siderestricted part 42 and the spring member side restricting part 83 arerespectively formed in a spherical protruded part and in a sphericalrecessed part. This construction serves as an aligning function in whichtheir respective axial centers are shifted so as to coincide with eachother. Therefore, even when the rotor shaft side restricted part 42fluctuates, the position (area) where the spherical protruded part ofthe rotor shaft side restricted part 42 abuts with the sphericalrecessed part of the spring member side restricting part 83 can convergeto near the bottom part of the spherical recessed part.

In addition, the rotor shaft side restricted part 42 is worked to becomethe spherical protruded part by using barrel polishing, and the springmember side restricting part 83 is formed such that the sphericalrecessed part is formed on the spring part 81 by only using a punch orthe like. Therefore, both the restricted part 42 and the restrictingpart 83 can be formed without using additional component parts and, asdescribed above, both the restricted part 42 and the restricting part 83can be simply worked without requiring a special tool and can be formedat a low cost. The working for the spherical protruded part of the rotorshaft side restricted part 42 and the working for the spherical recessedpart of spring member side restricting part 83 are not limited to theabove-mentioned working method.

The motor 1 structured as described above is rotated such that the rotormagnet 5 (permanent magnet 51, 52) is rotatably urged due to themagnetic interaction between the stator part 3 and the rotor magnet 5(permanent magnet 51, 52) by applying a prescribed electric current tothe coils 35, 36 of the stator part 3, and the rotor shaft 4 fixed tothe rotor magnet 5 is rotated. Further, in the first embodiment of thepresent invention, when the rotor shaft 4 is rotated, the lead screwpart of the shaft 10 provided at the one end of the rotor shaft 4 isrotated in an integral manner to move a body to be fed (not shown in thedrawing) in the axial direction which is engaged with the lead screwpart. The operation of the motor 1 and the body to be fed by the motor 1is similar to that of a conventional well-known motor and the like, andthus detailed description is omitted.

When the motor is rotated, the fluctuation of the rotor shaft 4 mayoccur due to the positioning errors or the like between the rotor magnet5 (permanent magnets 51, 52) and the stator part 3, and theabove-mentioned striking noise and sliding noise may occur between therotor shaft 4 and the radial bearing 6, the bearing 7 or the like.

However, in the motor 1 in accordance with the first embodiment of thepresent invention, the spring part 81 abuts with the one end of therotor shaft 4 to urge the rotor shaft 4 in the axial direction and theradial direction. In addition, the spring part 81 is provided with therotor shaft side restricted part 42 formed in the spherical protrudedpart and the spring member side restricting part 83 formed in thespherical recessed part which holds the rotor shaft side restricted part42. Therefore, even when the rotor shaft 4 is fluctuated in the radialdirection, the fluctuation of the rotor shaft 4 in the radial directionis regulated by the spring part 81 or by both the rotor shaft siderestricted part 42 and the spring member side restricting part 83, andthus the vibration is restrained and the occurrence of striking noise isrestrained.

Further, in the first embodiment of the present invention, the rotorshaft side restricted part 42 and the spring member side restrictingpart 83 are formed in the spherical protruded part and in the sphericalrecessed part which holds the spherical protruded part. Therefore, likean example that, when a ball is rolled along the circumferential surfaceof a hemispheric receptacle, the ball is finally moved to the bottom ofthe hemispheric receptacle, this means a type of aligning function inwhich the respective axial centers are automatically aligned with eachother. Therefore, the position (area) where the spherical protruded partof the rotor shaft side restricted part 42 abuts with of the sphericalrecessed part of the spring member side restricting part 83 converges tonear the bottom of the spherical recessed part of the spring member siderestricting part 83.

The motor 1 in accordance with the first embodiment of the presentinvention is provided with the rotor shaft side restricted part 42formed in the spherical protruded part at the one end of the rotor shaft4 and the spring member side restricting part 83 formed in the sphericalrecessed part for holding the spherical protruded part of the rotorshaft side restricted part 42. Therefore, even when the rotor shaft 4 isfluctuated in the radial direction, the fluctuation of the rotor shaft 4in the radial direction is regulated by both the rotor shaft siderestricted part 42 and the spring member side restricting part 83, andthus the vibration can be restrained and the occurrence of strikingnoise can be restrained.

Further, in the first embodiment of the present invention, the rotorshaft side restricted part 42 and the spring member side restrictingpart 83 are respectively formed in the spherical protruded part and inthe spherical recessed part, which serves as an aligning function inwhich their respective axial centers are aligned so as to coincide witheach other. Therefore, even when the rotor shaft side restricted part 42is fluctuated, the position (area) where the spherical protruded part ofthe rotor shaft side restricted part 42 abuts with the sphericalrecessed part of the spring member side restricting part 83 can beconverged to near the bottom part of the spherical recessed part.Accordingly, the vibration and the occurrence of striking noise can berestrained.

In addition, the rotor shaft side restricted part 42 is worked to be thespherical protruded part by using barrel polishing, and the springmember side restricting part 83 is formed such that the sphericalrecessed part is formed on the spring part 81 by using a punch or thelike. Therefore, both the restricted part 42 and the restricting part 83can be formed without using additional component parts and, as describedabove, both the restricted part 42 and the restricting part 83 can besimply worked without requiring a special tool and can be formed at alow cost.

Further, the spring part 81 of the spring member 8 urges a part of theouter peripheral face of the rotor shaft 4 to bring into contact with apart of the inner peripheral face of the bearing part 61 of the radialbearing 6. Therefore, since the rotor shaft 4 is urged by the spring inthe radial direction, the fluctuation of the rotor shaft 4 is regulatedin the contacting direction, and thus the vibration is restrained andthe occurrence of striking noise is restrained.

The results of the noise evaluations of a motor in accordance with thefirst embodiment of the present invention and a conventional motor whenthe respective motors are rotated are as follows. These motors are usedfor a video camera or a digital camera.

1) a motor in accordance with the first embodiment of the presentinvention . . . 28-30 dB-A.

The sound of “rattling” peculiar to the striking noise is not generated.

2) a conventional motor . . . 34-37 dB-A.

The sound of “rattling” particular to the striking noise is generated.As described above, in the motor in the first embodiment of the presentinvention, the occurrence of the striking noise is restricted and noisesduring rotation are reduced in comparison with the conventional motor.

The motor in accordance with the first embodiment of the presentinvention is provided with the rotor shaft side restricted part and thespring member side restricting part. Therefore, the contact (sliding)area is increased in comparison with the structure of the conventionalmotor, and thus the sliding noises may increase to some extent. However,according to the motor in accordance with the first embodiment of thepresent invention, the occurrence of striking noise is restrained and,as a result, noises during rotation are reduced in comparison with theconventional motor.

The present invention has been described in detail using thisembodiment, but the present invention is not limited to the embodimentdescribed above and many modifications can be without departing from thepresent invention.

Next, a motor in accordance with a second embodiment of the presentinvention will be described with reference to FIG. 6, in which a rotorshaft side restricted part 42 and a spring member side restricting part83 are provided to regulate the fluctuation of the rotor shaft 4 in theradial direction. FIG. 6 is an enlarged view showing the rotor shaftside restricted part 42 and the spring member side restricting part 83in accordance with the second embodiment of the present invention. Inthe second embodiment of the present invention, the same notationalsymbols are used for the same constructing members as the firstembodiment and their description is omitted.

A spring member 8A shown in the second embodiment of the presentinvention is formed of one piece of a metal plate similarly to thespring member 8 shown in the first embodiment and fixed at a prescribedposition of the motor case 39 by welding. A spring part 81A for abuttingwith one end of the rotor shaft 4 is formed in the spring member 8A soas to extend on the inner side from the center hole 82. The differencebetween the second embodiment from the first embodiment is that thespring part 81A is provided with a bent part 84 for adjusting theposition of the spring member side restricting part 83 abutting on theshaft center line 4 a of the rotor shaft 4 (rotor shaft side restrictedpart 42).

The bent part 84 is formed at a position near the spring member siderestricting part 83 of the spring part 81A so as to be substantiallyparallel to the direction perpendicular to the shaft center line 4 a ofthe rotor shaft 4. According to the construction described above, thespring member side restricting part 83 formed in the spherical recessedpart can be arranged such that the center 83 b of the spherical recessedpart is positioned at the center 42 a of the rotor shaft side restrictedpart 42, i.e., on the shaft center line 4 a of the rotor shaft 4. Thespring member side restricting part 83 of the spring part 81A urges therotor shaft side restricted part 42 in the axial direction of the rotorshaft 4 as shown in FIG. 6. In the second embodiment of the presentinvention, similarly to the first embodiment, the diameter of thespherical recessed part of the spring member side restricting part 83 isset to be larger than that of the spherical protruded part of the rotorshaft side restricted part 42. Therefore, the center 42 a of thespherical protruded part of the rotor shaft side restricted part 42 iscapable of abutting with the center 83 b of the spherical recessed partof the spring member side restricting part 83.

The spring member 8A in accordance with the second embodiment of thepresent invention is formed by press working, which is punching the rawmaterial of a thin plate. At this time, a bending process issimultaneously applied to the spring part 81A to form the bent part 84.The bent part 84 is formed by the bending process with a high degree ofaccuracy. If required, at the time of assembling or the like, the bentpart 84 may be adjusted such that the spring member side restrictingpart 83 abuts on the shaft center line 4 a of the rotor shaft 4 (rotorshaft side restricted part 42). Further, in the second embodiment of thepresent invention, the center 83 b of the spherical recessed part of thespring member side restricting part 83 is formed so as to coincide withthe center 42 a of the rotor shaft side restricted part 42, i.e., theshaft center line 4 a of the rotor shaft 4. However, the presentinvention is not to be limited to the second embodiment. Concretely,judging from the starting torque, similar effects may be obtained evenwhen the center 83 b of the spherical recessed part of the spring memberside restricting part 83 abuts with the rotor shaft side restricted part42 at a position deviated to about 10° from the shaft center line 4 a ofthe rotor shaft 4.

The motor in accordance with the second embodiment of the presentinvention is also constructed, similarly to the motor 1 in the firstembodiment, such that the spring part 81 abuts with one end of the rotorshaft 4 to urge the rotor shaft 4 in the axial direction. In addition,the motor in accordance with the second embodiment is provided with therotor shaft side restricted part 42 formed in the spherical protrudedpart and the spring member side restricting part 83 formed in thespherical recessed part which holds the rotor shaft side restricted part42. Therefore, even when the rotor shaft 4 is fluctuated in the radialdirection, the fluctuation of the rotor shaft 4 in the radial directionis regulated by the spring part 81A or both the restricted part 42 andthe restricting part 83. Accordingly, the vibration and the occurrenceof the striking noise are restrained.

In addition, in the second embodiment of the present invention, thespring member side restricting part 83 urges the rotor shaft siderestricted part 42 in the axial direction of the rotor shaft 4. In otherwords, the spring member side restricting part 83 formed in thespherical recessed part is disposed such that the center 83 b of thespherical recessed part of the spring member side restricting part 83conincides with the center 42 a of the rotor shaft side restricted part42, i.e., the shaft center line 4 a of the rotation shaft 4. Therefore,the length from the shaft center line 4 a of the rotor shaft 4 in theradial direction becomes smaller than that in the first embodiment ofthe present invention. Accordingly, the occurrence of the striking noiseis restrained and the occurrence of an excessive load torque can berestrained at the time of starting.

In other words, as described above, in the first embodiment of thepresent invention, the spring member side restricting part 83 abuts withthe rotor shaft side restricted part 42 at the position deviated fromthe center of the rotor shaft 4. Therefore, when the motor 1 is started,a torque is generated which is proportional to the distance in theradial direction from the shaft center line 4 a to the abutting positionof the rotor shaft 4. In addition, the rotor shaft 4 slides on thebearing part 61 of the radial bearing 6 and the frictional resistance isgenerated, which causes a load torque at the time of staring of themotor. Accordingly, the motor 1 in the first embodiment of the presentinvention requires a higher torque to start than the starting torquethat is required to merely rotate the rotor shaft 4.

On the other hand, in the motor in accordance with the second embodimentof the present invention, since the spring member side restricting part83 urges the rotor shaft side restricted part 42 in the axial directionof the rotor shaft 4, the spring member side restricting part 83 abutswith the rotor shaft side restricted part 42 at the center position(shaft center line 4 a) of or near the rotor shaft 4. Therefore, theload torque described above can be reduced and the starting torquerequired to start rotating at the time of stoppage can be reduced andthus the starting performance of the motor can be improved. For example,in the motor of the second embodiment, the starting voltage at the timeof staring is reduced to 1.3 V from 1.6 V. In addition, since the bentpart 84 is formed by press working, the bent part 84 can be simplyworked without adding a separate component part and thus can be formedat a low cost. Further, if needed, since the bent part 84 can beadjusted such that the spring member side restricting part 83 abuts withthe rotor shaft side restricted part 42, simple adjustment can beobtained.

The bent part 84 is formed by bending in a press working process but thepresent invention is not limited to this method. For example, the bentpart may be formed in a curved shape at the time of press working. Theimportant matter is that the center part 83 b of the spring member siderestricting part 83 abuts with the center 42 a of the rotor shaft siderestricted part 42 and the spring member side restricting part 83 isadjusted so as to urge the rotor shaft 4 in the axial direction.

Further, in the second embodiment of the present invention, the bentpart 84 is formed in the spring part 8A and the spring member siderestricting part 83 urges the rotor shaft side restricted part 42 in theaxial direction of the rotor shaft 4. However, alternatively, the bentpart 84 may not be provided in the spring part 8A, the rotor shaft 4 isextended in the axial direction and the spring member side restrictingpart 83 urges the rotor shaft side restricted part 42 in the axialdirection of the rotor shaft 4.

FIGS. 3(a) through 3(d) are enlarged views showing the rotor shaft siderestricted part and the spring member side restricting part inaccordance with other embodiments of the present invention. FIGS. 4(a)through 4(d) are enlarged views showing the rotor shaft side restrictedpart and the spring member side restricting part in accordance withother embodiments of the present invention. FIGS. 3(a) through 3(d) andFIGS. 4(a) through 4(d) are each different directional views from thatin FIG. 2.

In FIG. 3(a), the rotor shaft side restricted part 42 a is formed in aspherical shape and the spring member side restricting part 83 a isformed in a V-shape in a cross-sectional view. According to thestructure described above, the fluctuation of the rotor shaft 4 can beregulated in the radial direction different from the radial directionurged by the spring part 83 a. The spring member side restricting part83 a in accordance with the embodiment of the present invention can beformed by only bending a spring part made of a flat plate in the V-shapein the cross-sectional view. Therefore, the spring member siderestricting part 83 a can be simply and easily worked without requiringa special tool.

FIG. 3(b) is a view in which the rotor shaft side restricted part 42 bis formed in a spherical shape and the spring member side restrictingpart 83 a is formed in a spherical recessed part. The embodiment shownin FIG. 3(b) is similar to the above-mentioned embodiment and thus itsdescription is omitted.

FIG. 3(c) is a view in which the rotor shaft side restricted part 42 cis formed in a spherical shape and the spring member side restrictingpart 83 c is formed in an aperture part having a smaller diameter thanthe outer diameter of the rotor shaft side restricted part 42 c.Therefore, the aperture part of the spring member side restricting part83 c regulates the outer diameter portion of the spherical rotor shaftside restricted part 42 c. According to the structure described above,the spring member side restricting part 83 c can be formed to besubstantially the same height without protruding from the sphericalcenter part of the rotor shaft side restricted part 42 c. Therefore, thespring member side restricting part 83 c does not protrude in the axialdirection and thus the motor can be made thinner.

In FIG. 3(d), the rotor shaft side restricted part 42 d is formed in aspherical shape and the spring member side restricting part 83 d isformed in a conical shape. Therefore, the spring member side restrictingpart 83 d abuts with the rotor shaft side restricted part 42 d in a facecontact manner and thus the holding performance of the rotation shaftcan be further satisfactorily maintained.

In FIG. 4(a), the rotor shaft side restricted part 42 e is formed in agenerally conical shape having a spherical tip end part and the springmember side restricting part 83 e is formed in a recesses-projectionssurface in a wavy shape for holding the spherical tip end part of therotor shaft side restricted part 42 e. Therefore, the spring member siderestricting part 83 e is engaged with the tip end of the rotor shaftside restricted part 42 e at a concaved face part, and thus the rotorshaft side restricted part 42 e can be easily held and the positioningof the rotor shaft side restricted part 42 e can be easily performed.

In FIG. 4(b), the rotor shaft side restricted part 42 f is formed in aspherical shape and the spring member side restricting part 83 f isformed such that an annular member made of resin is fixed on a thinplate member. The inner diameter of the aperture of the resin annularmember is set to be smaller than the outer diameter of the rotor shaftside restricted part 42 f. Thus, the spring member side restricting part83 f holds the rotor shaft side restricted part 42 f such that theaperture part of the resin annular member regulates the outer diameterpart of the spherical rotor shaft side restricted part 42 f similarly tothe embodiment shown in FIG. 3(c). The spring member side restrictingpart 83 f is formed to be substantially the same height as the rotorshaft side restricted part 42 f without protruding from the sphericalcenter part of the rotor shaft side restricted part 42 f. Therefore,since an increase in the thickness of the spring member side restrictingpart 83 f is not required, thus the motor can be thinner. In addition,since the resin annular member is adhered to the abutting portion withthe rotor shaft side restricted part 42 f, the metal and the resin areabutted with each other and thus durability is excellent, which isdifferent from the case of abutting with metal and metal like theabove-mentioned embodiments.

FIG. 4(c) is a view showing an improved embodiment of that in FIG. 4(b). In FIG. 4(c), the rotor shaft side restricted part 42 g is formedin a spherical shape and the spring member side restricting part 83 g isformed such that a resin annular member is insert-molded in a thin platemember. Also in this case, the spring member side restricting part 83 gcan be formed thinner and excellent in durability similarly to thespring member side restricting part 83 f in FIG. 4(b). In addition, thespring member side restricting part 83 g can be securely and easilyformed by insert-molding the resin annular member to the thin platemember.

In FIG. 4(d), a spherical recessed part is formed as the rotor shaftside restricted part 42 h and a spherical shaped protruded part isformed as the spring member side restricting part 83 h. The diameter ofthe spherical shaped protruded part 83 h is formed to be smaller thanthe inner diameter of the spherical recessed part 83 h as the rotorshaft side restricted part 42 h similarly to the above-mentionedembodiments. The rotor shaft side restricted part 42 h is formed suchthat the center part of the rotor shaft side restricted part 42 h isprovided with a spherical concaved shape and the spherical protrudedpart 83 h is inserted and supported by the spherical concaved portion.Therefore, the space for the spring member side restricting part 83 hcan be reduced and the motor can be thinner.

The present invention is not limited to the embodiments shown in FIGS.3(a) through 3(d) and FIGS. 4(a) through 4(d), and any shape which iscapable of regulating the fluctuation of the rotation shaft 4 can beapplicable.

Further, the sliding loss may be reduced by applying a wearingresistance film, for example, performing fluorine coating at the areawhere the rotor shaft side restricted part 42 and the spring member siderestricting part 83 are brought into contact with each other. Inaddition, the embodiments shown in FIGS. 3(a) through 3(d) and FIGS.4(a) through 4(d) may be applied to the motor shown in the secondembodiment of the present invention.

While the description above refers to particular embodiments of thepresent invention, it will be understood that many modifications may bemade without departing from the spirit thereof. The accompanying claimsare intended to cover such modifications as would fall within the truescope and spirit of the present invention.

The presently disclosed embodiments are therefore to be considered inall respects as illustrative and not restrictive, the scope of theinvention being indicated by the appended claims, rather than theforegoing description, and all changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein.

1. A motor comprising: a rotor part having a rotor shaft and a rotormagnet; a stator part which is oppositely disposed to the rotor magnetvia a gap space; a bearing which rotatably supports the rotor shaft; aspring member which abuts with one end of the rotor shaft to urge therotor shaft in an axial direction; a spring member side restricting partwhich is provided in the spring member to prevent fluctuation in aradial direction of the rotor shaft; and a rotor shaft side restrictedpart which is provided in the rotor shaft and engages with the springmember side restricting part.
 2. The motor according to claim 1, furthercomprising: a spherical recessed part which is formed in one of therotor shaft side restricted part and the spring member side restrictingpart; and a spherical protruded part which is formed in the other of therotor shaft side restricted part and the spring member side restrictingpart.
 3. The motor according to claim 1, wherein the spring member urgesthe rotor shaft in the radial direction.
 4. The motor according to claim1, wherein the spring member side restricting part urges the rotor shaftside restricted part in the axial direction of the rotor shaft.
 5. Themotor according to claim 4, wherein the spring member is provided with abent part for adjusting a position where the spring member siderestricting part abuts with the rotor shaft side restricted part.
 6. Themotor according to claim 1, wherein the spring member side restrictingpart urges the rotor shaft side restricted part in the radial direction.7. The motor according to claim 6, wherein the spring member siderestricting part abuts with the rotor shaft side restricted part at aposition deviated from a shaft center line of the rotor shaft.
 8. Themotor according to claim 7, wherein the spring member side restrictingpart abuts with the rotor shaft side restricted part at a positiondeviated about angle θ=20° in the radial direction from the shaft centerline of the rotor shaft.
 9. The motor according to claim 8, wherein thespring member side restricting part is formed by a spherical recessedpart and the rotor shaft side restricted part is formed by a sphericalprotruded part.
 10. The motor according to claim 9, wherein a diameterof the spherical recessed part of the spring member side restrictingpart is set to be larger than a diameter of the spherical protruded partof the rotor shaft side restricted part.
 11. The motor according toclaim 1, wherein the rotor shaft side restricted part is formed in aspherical shape and an abutting part of the spring member siderestricting part with the rotor shaft side restricted part is formed inone of a V-shaped part, a spherical recessed part, an aperture part anda circular ring member.
 12. The motor according to claim 1, wherein therotor shaft side restricted part is formed in a spherical recessed partand the spring member side restricting part is formed in a sphericalprotruded part.
 13. A motor comprising: a rotor part having a rotorshaft and a rotor magnet; a stator part which is oppositely disposed tothe rotor magnet via a gap space; a bearing which rotatably supports therotor shaft; a spring member having a spring and a spring member siderestricting part; and a rotor shaft side restricted part which isprovided in the rotor shaft and engages with the spring member siderestricting part, wherein the spring member abuts with one end of therotor shaft to urge the rotor shaft in an axial direction, wherein aspring member side restricting part prevents fluctuation in a radialdirection of the rotor shaft.